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Kube

 
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David
Intermediate Contributor 75+


Joined: 11 Jun 2003
Posts: 90
Location: Canada

PostPosted: Mon Aug 11, 2003 7:57 pm    Post subject: Kube Reply with quote

Anybody try the Kef Kube. I understand it is basically an equalizer that works at low frequencies. I saw some on ebay sold for about $50 US.

Somehow it hooks up through the tape monitor circuit, but I don't understand how the signal goes back to the amp. Do you need two tape monitors?

David
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proffski
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Joined: 22 Aug 2003
Posts: 1296
Location: Tewkesbury UK

PostPosted: Sat Aug 23, 2003 1:30 pm    Post subject: Re: Kube Reply with quote

Depends which KEF KUBE. There were several models, 100, 200, 107, 107/2... Maybe even more!

The best is probably the 107/2. If you have a tape in/out in your amplifier the cube siply loops through the circuitry. I find that until I build a subwoofer that the 107/2 can make a fantastic positive increase to the sound. However, some purists may disagree with me on this on. I have just upgraded from the 100 to the 107/2 and just ordered another from a dealer. Verdict? BRILLIANT!
David wrote:
Anybody try the Kef Kube. I understand it is basically an equalizer that works at low frequencies. I saw some on ebay sold for about $50 US.

Somehow it hooks up through the tape monitor circuit, but I don't understand how the signal goes back to the amp. Do you need two tape monitors?

David

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The Rang
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Joined: 27 Jul 2005
Posts: 7
Location: Vancouver, Canada

PostPosted: Wed Jul 27, 2005 2:27 am    Post subject: Reply with quote

I have a pair of 1985 104.2, non bi-wire.

Is the 104.2 Kube most appropriate for my application?

The Kube 200 has high and low controls. I'm assuming that's for biwired speakers. Am I correct?

Very little information out there
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ColinR
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Joined: 31 Jul 2004
Posts: 1175
Location: Staffordshire

PostPosted: Wed Jul 27, 2005 1:59 pm    Post subject: Reply with quote

Not interested in 104-2's myself as they are not "user repairable" but from my stock of "useless" KEF information.

The KUBE 200 provides fixed equalisation which extends the loudspeakerís bass response below its normal, unequalised cut-off point.

On the 104/2 the bass cut-off is extended from 55Hz to 20Hz @ -6dB.

It offers variable low and high frequency parametric equalisation.

The HF Contour control adjusts the high frequency level above 1kHz, while the LF Contour control adjusts the low frequency level below 160Hz, controlling the balance between bass and midrange.

The LF Contour control applies equalisation to compensate for the actual effects of room boundaries on the perceived bass response of the speaker.

DO NOT USE HIGH LEVELS WHEN THE EQ IS SWITCHED IN as there is every chance you will over extend the bass drivers to the point where they are damaged.

Cone excursion is significantly increased even at low levels so THINK when using a Kube with older examples of speaker which may be suffering from foam rot.

It has enough inputs and outputs for passive biampification, however you can just stick it into an amplifier's tape monitor loop via the DIN socket and the tape machine into the back of the Kube and adjust the level control for "normal" operation.
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The Rang
Introductory Contributor


Joined: 27 Jul 2005
Posts: 7
Location: Vancouver, Canada

PostPosted: Thu Jul 28, 2005 1:28 am    Post subject: Reply with quote

ColinR wrote:
Not interested in 104-2's myself as they are not "user repairable" but from my stock of "useless" KEF information.

The KUBE 200 provides fixed equalisation which extends the loudspeakerís bass response below its normal, unequalised cut-off point.

On the 104/2 the bass cut-off is extended from 55Hz to 20Hz @ -6dB.

It offers variable low and high frequency parametric equalisation.

The HF Contour control adjusts the high frequency level above 1kHz, while the LF Contour control adjusts the low frequency level below 160Hz, controlling the balance between bass and midrange.

The LF Contour control applies equalisation to compensate for the actual effects of room boundaries on the perceived bass response of the speaker.

DO NOT USE HIGH LEVELS WHEN THE EQ IS SWITCHED IN as there is every chance you will over extend the bass drivers to the point where they are damaged.

Cone excursion is significantly increased even at low levels so THINK when using a Kube with older examples of speaker which may be suffering from foam rot.

It has enough inputs and outputs for passive biampification, however you can just stick it into an amplifier's tape monitor loop via the DIN socket and the tape machine into the back of the Kube and adjust the level control for "normal" operation.


Thanks Colin,

This is very helpful.

I have heard of "foam rot" on older 104.2's but am not sure what people mean. The surrounds on my woofers are a black rubber-like material.
There is however a 2.5 inch foam doughnut (for lack of a better term) in the centre near the rod.

On the Kube 200 how does one accurately adjust for the various KEF models?
For example, the KUBE 104.2 will be designed with that specific 55hz cut off point in mind.

Thank you in advance, Blair
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ColinR
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Joined: 31 Jul 2004
Posts: 1175
Location: Staffordshire

PostPosted: Thu Jul 28, 2005 9:05 pm    Post subject: Reply with quote

There were two surrounds used in the later Ref Series foam and rubber, so you'll get away with one problem but once the donut starts to degrade (grey dust, flakes and small bits will drop off), you'll get a leak and the bass will begin to sound lumpy.
The problem is most current speaker rebuilders (even KEF!), prefer to run rather than repair, so in the future many force cancellation rods will be binned and the cabinets "beefed up" in other ways to maintain cabinet rigidity.

55Hz? No, "the LF Contour adjusts the low frequency level below 160 Hz," so it will cover all three KEF models, 102, 103/3 & 104-2.
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clem_o
Intermediate Contributor 25+


Joined: 30 May 2005
Posts: 44
Location: Manila, the Philippines

PostPosted: Wed Aug 10, 2005 4:51 am    Post subject: Reply with quote

I have a KEF100 and have tried ths on both the 104/2 and 105/3. I tend to agree with some others who have observed that the equalizer isn't very transparent in the mids and highs (specially the latter) - perhaps because of the NE5532s in it? Anyway somene suggested going bi-amp and inserting the Kube into the LF amplifier. I think this is the way to go (if you do have a spare amplifier. The 104/2 is 'ready' for such a setup anyway, given the separate connectors for the LF and MF/HF drivers).

Cheers!
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proffski
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Joined: 22 Aug 2003
Posts: 1296
Location: Tewkesbury UK

PostPosted: Tue Aug 30, 2005 1:06 pm    Post subject: Reply with quote

Let me know how you get on, I have Kube 107/2.
I switch it in for some recordings, by careful adjustment it can work quite well, in other recordings it certainly masks detail.

It is excellent at low level night time listening however; I did toy with the idea of replacing the op-amps with better ones.
Sadly they are not in sockets and I doubt my own ability to desolder from a double sided PCB without causing damage.

Good luck!
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clem_o
Intermediate Contributor 25+


Joined: 30 May 2005
Posts: 44
Location: Manila, the Philippines

PostPosted: Mon Dec 05, 2005 4:27 am    Post subject: Reply with quote

Hi proffski,

I've done some modes on the Kube 100 - changed the op-amps to OPA2134s, and removed an input capacitor (470pF) on each channel. Definite benefits in transparency, though still not as good as bypassed.

It was VERY difficult to desolder the op-amps - not sure how that PCB is made, but it does very well in absorbing and distributing the heat. I wanted to save the original 5532s; if you are willing to sacrifice them, then snipping off the legs and pulling them out one by one will make the modification job a lot easier to do.

Just note that only the OPA2604s can handle the supply voltages, which are set at +-20V. If you want to use some other dual-stage opamp, you'll have to drop the supply voltages as well.

Oh, one more: the Kube100 has a little circuit that mutes the inputs when the supply voltage hasn't reached +-20. If you decide to mode the supply voltage, you'll have to find a way to disable the muting circuit as well...
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proffski
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Joined: 22 Aug 2003
Posts: 1296
Location: Tewkesbury UK

PostPosted: Mon Dec 05, 2005 8:59 am    Post subject: Reply with quote

Cheers!
I'll consider having a bash over Christmas vacation.
MY Kube is littered with regulators so possibly ok for the replacement op-amps. Will use turned pin IC sockets.

A.
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